In the related art, Al or an Al alloy is widely used as a wiring film such as a flat panel display including a liquid crystal and an organic EL panel, or a touch panel. In recent years, it has been required that the wiring film be miniaturized (has a narrow width) and have a small thickness, and a wiring film having a lower specific resistance than the wiring film in the related art is desired.
Therefore, a wiring film using copper or a copper alloy, which is a material having a lower specific resistance than Al or an Al alloy, is provided in order to meet the demand for miniaturization and a small thickness of the wiring film as described above.
A sputtering method using a sputtering target is generally used when forming such a wiring film (thin film) of copper or a copper alloy on a substrate.
As the sputtering target described above, a flat sputtering target disclosed in Japanese Patent No. 4974198 or a cylindrical sputtering target disclosed in Japanese Unexamined Patent Application, First Publication No. 2012-111994 has been proposed.
Herein, the cylindrical sputtering target has an outer peripheral surface as a sputtering surface and the sputtering is performed while rotating the target. Accordingly, the sputtering using the cylindrical sputtering target is suitable for continuous film formation compared to a case using a flat sputtering target, and excellent efficiency in use of the target is obtained.
As disclosed in Japanese Unexamined Patent Application, First Publication No. 2012-111994, the cylindrical sputtering target described above is manufactured by performing a hot working step (hot rolling step and hot extrusion step), a drawing step, and an annealing step. That is, in the related art, a cylindrical shape is formed by performing working by heating a columnar ingot to a predetermined temperature which is equal to or higher than a recrystallizing temperature, and then a cylindrical sputtering target having a predetermined shape is formed by further performing working and a heat treatment.